1. Field of the Invention
The present invention relates to video game processing. More particularly, the present invention relates to displaying a virtual space from a virtual viewpoint on a screen.
2. Description of the Related Art
A role playing game (called “RPG” hereinafter) is known as one video game genre. In a RPG, a character plays a role in a game instead of a player. In general, the player experiences a pseudo adventure through a character manipulated by the player (called “player character” hereinafter) so as to develop a story. In many cases, a player character and characters fighting against the player character (called “enemy character” hereinafter) are set in zones formed in a virtual space. The player character advances to each zone, where the player character fights against the enemy characters that prevent the player character from achieving his/her goal in the story. In addition, the player character obtains items that provide advantages during the fights and defeats the enemy character so as to develop the story.
In order to display an image from a certain viewpoint in a video game machine for implementing an RPG by displaying objects such as a player character and an enemy character in a virtual space on a screen, an object to be hidden behind a predetermined object is not displayed. For example, Z-buffer processing is used for removing hidden-parts. As a technology relating to the Z-buffering, an image synthesizing apparatus and an image synthesizing method are disclosed in Japanese Unexamined Patent Publication No. 8-161526, for example.
However, multiple characters may be required to be displayed on a single screen in a conventional RPG. As a result, a processing amount involved in the Z-buffering is increased. Thus, there is a problem that the number of displayed characters may be limited due to the processing capacity of the game machine. Similarly, when a character is required to be displayed in more detail, the number of polygons forming the character tends to increase. As a result, a processing amount involved in the Z-buffering increases as the number of polygons increases. Then, there is a problem that a number of polygons that can be used for other characters may be limited.